(CNN) The first US shipment of recently directed security assistance has arrived in Ukraine, the US Embassy in Kyiv tweeted Friday night.
The shipment "includes close to 200,000 pounds of lethal aid, including ammunition for the front line defenders of Ukraine," according to the tweet.
The development comes as the US has sought to convince Moscow to de-escalate the situation at the Ukrainian border, where Russia has amassed more than 100,000 troops.
US Secretary of State Antony Blinken warned Friday that any Russian invasion of Ukraine would be "met with a severe and a united response."
Blinken held a 90-minute bilateral meeting Friday in Geneva with Russian Foreign Minister Sergey Lavrov, the latest round of diplomatic talks that the US secretary said provided a "clearer path of understanding each other's concerns."
President Joe Biden said Wednesday that he believed Russian President Vladimir Putin would invade Ukraine. The US has warned that it will impose severe consequences in the event of an invasion -- and Blinken reiterated Friday that meant Russian troops crossing the border.
"We've been clear. If any Russian military forces move across Ukraine's border, that's a renewed invasion. It will be met with swift, severe and a united response from the United States and our partners and allies," Blinken said.
Lavrov insisted Friday that Russia was not planning to attack.
The Defense Department is working on a series of military options for Biden's approval that could be activated to beef up the US military presence in Eastern Europe as a deterrence if Russia invades Ukraine, according to two defense officials. "We are exploring a wide range of options on how we would bolster our allies militarily," the first official said.
These options would also likely be supported by sanctions.
The goal of any military reinforcement in Eastern Europe would be to provide deterrence and reassurance to allies. The options could include "movement of assets and forces already in Europe and also assets and forces available outside of Europe," the official said. A Russian invasion "certainly would be one trigger" for US troops and assets to move. But some forces might be used in exercises and other training scenarios as well.
Broadly, the US military goal would be to "meet the capability" that NATO allies in the region are asking for, the official said. US forces could operate, as they already do, unilaterally in Europe, but could also operate under existing NATO command structures.